The present invention generally relates to broadcasting systems and more specifically to a method and system for providing faster channel switching in a broadcasting system. Viewers of digital programs often experience significant delay when switching from one digital program to the next. In a digital cable or satellite system, program or channel switching is often handled by a set top box (STB). Typically, when a STB switches to a different program, there will be a 0.5 s to 1 s delay before the desired program is displayed. This delay is caused by current limitations in real-time broadcasting systems.
For example, in a Moving Picture Experts Group (MPEG)-based system, video frames are typically compressed into three type of frames, namely, “I” frame, “B” frame, and “P” frame. An I-frame is the first frame of a sequence of frames that may depend on the I-frame either directly or indirectly as a reference frame. Thus, a transmission may include I frames, each followed by a sequence of dependent frames. I-frames may occur in a transmission, for example, once every 0.5 second. Usually, an I-frame has a relatively low compression ratio. Dependent frames may include P-frames and B-frames. A P-frame is encoded by reference to a past reference frame, which may be an I-frame or a P-frame. A B-frame is encoded by reference to a past reference frame, a future reference frame, or both a past and a future reference frame. Again, a reference frame may be an I-frame or a P-frame. Since I-frames are used as reference frames for subsequent P-frames and B-frames in such a broadcast system, a video program cannot be displayed correctly without any I-frames. One of the ways to reduce the delay between program switch is to insert more I-frames. The insertion of additional I-frames, however, means requiring more bandwidth in order to transmit one video program, and thus leads to a less efficient system.
Hence, it would be desirable to provide a method and system that is capable of achieving faster channel switch without sacrificing bandwidth performance.